--- mformat.c
+++ mformat.c
@@ -1160,6 +1160,7 @@
 		}
 		read(fd, buf, blocksize);
 		keepBoot = 1;
+                close(fd);
 	}
 	if(!keepBoot && !(used_dev.use_2m & 0x7f)) {
 		memset((char *)boot, '\0', Fs.sector_size);